This invention relates to an electrical connector including a first connector having a plurality of electric contacts and a second connector having a plurality of electric contact elements adapted to electrically contact the electric contacts of the first connector when first and second connectors are connected, and more particularly to a contact construction of an electrical connector for electrically connecting electric contacts and electric contact elements of first and second connectors of the electrical connector.
One of hitherto used electrical connectors as shown in FIG. 26 includes a first connector plate 10 and a second connector plate 20 which are brought into a detachable abutment against each other to electrically connect a plurality of electric contacts 11 made of hemispherical protrusions of solder or the like provided on one surface of the first connector plate 10 to a plurality of electric contact elements 21 provided on one surface of the second connector plate 20. Such an electrical connector has a plug and socket mechanism (not shown) for detachably connecting the first and second connector plates 10 and 20.
The first connector plate 10 is made of a ceramic or hard resin board having a rigidity and the second connector plate 20 is also made of a hard resin plate having a rigidity. The electric contact element 21 is a pin having a flange 22 and telescopically received in a contact element cylinder 30 made of a metallic material such that the pin is urged toward the electric contact 11 by an elastic member 31 such as a coil spring located in the cylinder 30. With such an electrical connector, in general, the electric contacts 11 abut against or slidably contact electric contact elements to be electrically connected to each other.
Such an electrical connector has the following disadvantages.
(1) The construction for supporting the electric contact elements 21 is complicated to increase its manufacturing cost. PA0 (2) Owing to the construction for supporting the electric contact elements 21, the second connector plate 20 requires substantial spaces on its both sides which make it difficult to compact the electrical connector. Moreover, the contact element cylinders 30 for receiving therein the electric contact elements also somewhat require spaces which make it difficult to arrange the electric contact elements in high density. PA0 (3) In order to avoid the disadvantage described in (2), it may be devised to provide metal foils as electric contact elements 41 on one surface of the board 40 as shown in FIG. 27. In the case providing such metal foils on the board 40, there is a risk of the electric contacts 11 and electric contact elements 41 incorrectly contacting each other due to the difference in height between the electric contacts 11 of the first connector plate 10. PA0 (4) Furthermore, even if an impedance value, for example, of the order of 50.OMEGA. is desired between the electric contact elements 21 and grounding or earthing system (including a case having other grounding electric contact elements), the contact element cylinders 30 and the elastic members 31 would be constructionally longer with the construction shown in FIG. 26. Moreover, it may be difficult to ensure the impedance of the order of 50.OMEGA. with the dielectric constant .epsilon..sub.0 of the air and the relative dielectric constant .epsilon..sub.1 of a hard resin plate. PA0 (1) The electrical connector of this type has no means for securely urging the metal layers 331 of the flexible printed card board 324 to the pads 342 of the board 340. Moreover, the flexible printed card board 324 is inferior in followability, causing incorrect contact between the electric contacts and electric contact elements. PA0 (2) When the metal layers 331 of the flexible printed card board 324 are urged to the pads 342 of the board 340, the metal layers 331 could not accommodate the difference in height between the pads 342. Further, there is no means for ascertaining whether the soldered surfaces are correct so that there is a risk of the adjacent leads being bridged by solder. PA0 (3) When the bit-insert 376 of the prior art is connected to the board 340 by soldering, there is a tendency for the air 378 to enter the soldered surfaces as shown in FIG. 31, causing defects or irregularities of soldered surfaces. As a result, the strength of the soldered portions becomes lower to cause defective connection of the metal layers 331 to the flexible printed card board 324. PA0 (4) Once the metal layers 331 of the flexible printed card board 324 has been connected to the pads 342 of the board 340 by soldering, the board 340 itself must be replaced to increase the running cost when the electric contact elements 322 of the second connector 320 have been worn off by repeated connections to and disconnections from the first connector 310. PA0 (1) The board on which the electric contact elements are provided is partially cut to form slits closely around the electric contact elements, thereby elastically supporting them. Therefore, electrical connector can be manufactured with extremely low cost. Particularly, the manufacturing cost can be considerably reduced when the electric contact elements are made by the printed circuit forming method. PA0 (2) According to the invention a great number of electric contact elements can be formed on a second connector without requiring large space, so that the electrical connector can be compacted to a great extent in comparison with those of the prior art. Moreover, by forming the electric contact elements by means of the printed circuit producing method, it becomes easier to arrange them in higher density. PA0 (3) According to the invention, the electric contact elements are elastically supported by the elasticity of the inherent member without using any other mechanical parts, so that the electric contacts and the electric contact elements can achieve good contacting condition with high reliability without being affected by difference in height between the electric contacts. Particularly, in case of interposing the elastomer layer between the board on which the electric contact elements are formed and the back-up plate, the electric contact elements are supported in better elastic condition to obtain the more stable contact condition. PA0 (4) According to the invention, the metal conductors are provided on the board on the opposite side of the electric contact elements for grounding or earthing. In this case, the impedance between the electric contact elements for signals and earthing can be easily adjusted by applying the microstrip line design. For example, the impedance value of the order of 50.OMEGA. can be easily set which would be difficult in the prior art. PA0 (5) When the plate portion of the second connector is constructed only by a board formed with electric contact elements, the number of parts can be considerably reduced to lower the manufacturing cost. PA0 (6) According to the invention, the board of the second electrical connector is cut to form slits closely around the electric contact elements, while the board is made thinner over the area provided with the plurality of electric contact elements, thereby elastically supporting the electric contact elements. Moreover, the lead wires of the metal layers extend from the electric contact elements, and the metal conductors for earthing are provided on the board on the opposite side of the electric contact elements. Therefore, the electric contact elements are elastically supported, even if the entire thickness of the board is thick. Moreover, by applying the microstrip line design, the transmission losses are limited to the minimum to obtain a required impedance characteristic (for example, the impedance value of the order of 50.OMEGA.) with ease. PA0 (7) According to the invention, as only the parts of the board surrounded by the slits are made thinner, the board has a sufficient durability and the entire board can be made thinner or the space can be saved. PA0 (8) The features of the invention of providing the slits around the electric contact elements and thinner parts of the board surrounded by the slits can be applicable to electrical connector having boards. PA0 (9) According to the invention, by providing the projections on the housing, the followability is given to the flexible printed card board to avoid any defective connection. PA0 (10) By removing the part of the insulating layer in the proximity of the connection of the flexible printed card board and corresponding to the pads of the board, the positional shifting of lead portions can be visually ascertained and the soldered connections can be ascertained. PA0 (11) By removing the part of the insulating layer with exception of its end, the connections can be visually ascertained to easily maintain the accuracy of the pitch of the metal layers and to prevent the solder from bridging between the adjacent soldered portions. PA0 (12) By using the bit-inserts, the electric contact elements can be arranged in higher density on the board, and the housing can be easily removed from the block for cleaning the electric contact elements and other purposes. PA0 (13) According to the invention, by providing the recess in the bottom of the bit-insert, even if the air enters the soldering portions, it can escape into the recess to prevent defective or irregular soldering, thereby ensuring stable soldering and increasing soldering strength. PA0 (14) According to the invention, by providing the positioning pin, the electrical connector can be easily positioned on the board. PA0 (15) According to the invention the housing is provided with urging members in its projections at locations corresponding to the pads of the board. As a result, there is no need for soldering the flexible printed card board and pads of the board, and the second connector can easily be replaced when the electric contact elements of the second connector have been worn off due to repeated connections and disconnections. PA0 (16) According to the invention a board supporting the electric contact element is formed with slits for elastically supporting the electric contact elements, and the electric contact elements are inclined at an angle of .alpha. toward the electric contacts before they have contacted each other, and the electric contact elements are inclined at an angle of .beta. on the opposite side of the angle .alpha. with the relation of .alpha.&gt;.beta. when the electric contacts and electric contact elements have contacted each other. With this construction, even if the electric contacts are rolling, the stable connection can be achieved because of no accumulation of foreign substances at the rolling position. PA0 (17) With the construction achieving the relation of .alpha.&gt;.beta., the electric contacts of the first connector will contact the electric contact elements and move in one direction on the electric contact elements, and then return in opposite direction during which the inclined angle of the electric contact elements changes from .alpha. to .beta.. Therefore, the electric contacts remain stationary at the moment just before starting their returning movement. As a result, there are no accumulation of foreign substances at the locations where the electric contacts and the electric contact elements finally contact each other.
A plug and socket mechanism hitherto used is shown in FIGS. 28A and 28B to FIG. 31. As shown in FIG. 29, a first connector 310 and a second connector 320 are detachably connected by the plug and socket mechanism. The second connector 320 is embraced between a housing 372 and a block 374, and a flexible printed card board 324 extends from the housing 372 and the block 374 to be connected to pads 342 of a board 340.
With this electrical connector hitherto used, bolts 338 pass through the housing 372, the flexible printed card board 324, the block 374 and the board 340 having apertures 384 and are tightened by nuts 382 screwed onto the ends of the bolts 338, whereby these members are clamped as shown in FIG. 30A. As surface mounting components are mounted on the board 340 on the side of the nuts 382 and the apertures 384 of the board 340 are must be formed so as to avoid the area of the board 340 used for the wiring, there is a tendency for the board 340 to become large. To eliminate this problem, the bit-insert 376 has been devised which is able to be clamped by screw means, while permitting a connector to be mounted by the surface mounting method as shown in FIG. 30B.
The housing 372 is fixed by the bolts 338 to the block 74 having the bit-inserts 376 press-fitted therein. As shown in FIG. 28B, by fixing the metal layers 331 of the flexible printed card board 324 of the second connector 320 to the pads 342 of the board 340, the block 374 to which the second connector 320 and the housing 372 are fixed is mounted on the board 340. When the metal layers 331 are attached to the flexible printed card board 324 of the second connector 320 by soldering, the metal layers 331 are urged to the pads 342 of the board 340 as shown in FIG. 28B by means of a jig (not shown).
With this construction, the first connector 310 is inserted into a fitting opening 336 formed in the housing 372 to the second connector 320 secured to the board 340 and the block 374 to cause the electric contacts 312 of the first connector 310 to contact the electric contact elements 322 of the second connector 320. During such an operation, the first connector 310 is held being urged to the second connector 320 as by urging jig (not shown). Such a construction is referred to herein as "plug and socket mechanism".
The electrical connector having such a plug and socket mechanism suffers the following disadvantages.
On the other hand, if there are any contaminations or foreign substances 435 (FIG. 33A) on the electric contacts and electric contact elements, when they are caused to abut against each other, good connections therebetween could not be obtained. In order to overcome this problem, the sliding contact between the electric contacts and electric contact elements has generally been employed so that the contaminations or foreign substances on the contacting surfaces are wiped or removed by the relative movement between the electric contacts and electric contact elements.
FIG. 32 illustrates part of an electrical connector having an electric contact 412 and an electric contact element 422 to be slidably contact each other. FIG. 33A illustrates the electric contact 412 slidably moving from the position A to the position B, while moving in the direction shown by an arrow E. FIG. 33B simultaneously shows the electric contact 412 before and after it is slidably moved, respectively. FIG. 33C illustrates the electric contact 412 which is rolling as shown by an arrow F.
As shown in FIG. 32, the second connector 450 is formed with a slit 430 so that an electric contact element 422 supported by a small movable piece is lowered downwardly when the first connector 411 is urged against the second connector 450 in the direction shown by an arrow D. In more detail, the electric contact 412 of the first connector 411 contacts the electric contact element 422 of the second connector 450 at the point A at the first contacting moment as shown in FIG. 33A. Next, while the electric contact 412 is moving downwardly in the direction shown by the arrow E, the electric contact 412 slidably moves on the electric contact element 422 to the point B.
However, during such a sliding movement, the contaminations or foreign substances 435 are moved by the electric contact 412 in the sliding direction so as to accumulate higher. As a result, the electric contact 412 tends to ride over the accumulation so that the electric contact 412 is rolled or inclined to cause a defective connection between the electric contact 412 and the electric contact element 422.